We are developing a marketplace webapp which charges customers on behalf of sellers.
After reading through PayPal's API documentation, the only solution seems to be the Permissions service.
According to the documentation. After retrieving the access token and token secrete of a seller through the RequestPermissions call, we generated X-PAYPAL-AUTHORIZATION header to initiate an express checkout payment id. However, the payment id generated is associated with our PayPal account instead of the seller's, which is not the anticipated behavior.
Adding seller's email address in the SUBJECT field as noted in PayPal Name-Value Pair API Basics does work, but as we tested it, it has nothing to do with the access token and token secrete.
The problem with the SUBJECT field is that we cannot make sure the seller's email address with us is the one PayPal have on file.
The GetBasicPersonalData permission seems to be able to get a valid email address, but that needs to be pre-approved by PayPal. In fact, I have come across many websites that does not require this permission but able to initiate payment on behalf of other users. Is there a way to just get sellers' email or PayPal Id without GetBasicPersonalData permission? We don't actually need any other personal data except email or PayPal Id.